THE  CATALYTIC  REDUCTION  OF 
PARA  DIMETHYLAMINOPHENOL 


BY 

HERMANN  CONRAD  NIES  HECKEL 

B.S.  University  of  Illinois,  1921 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  MASTER  OF  SCIENCE  IN  CHEMISTRY 
IN  THE  GRADUATE  SCHOOL  OF  THE  UNIVERSITY 
OF  ILLINOIS,  1922 


URBANA,  ILLINOIS 


UNIVERSITY  OF  ILLINOIS 


THE  GRADUATE  SCHOOL 


May  27 192^. 


I HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 

s u PERVI SION  BY Hermann  0 oni^cL  Hies  Eec^ksl 

ENTITLED  „ JLe__(^tal3ry,c  ReMati  p-JDimatliylaininoplienol . 


BE  ACCEPTED  AS  EULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 


THE  DEGREE  OF 


in  Chemistry 


Recommendation  concurred  in* 


Committee 

on 

Final  Examination* 


^Required  for  doctor’s  degree  but  not  for  master’s 


^:990f>-3 


i 


aiuc 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/catalyticreductiOOheck 


I wish  to  express  my  sincere  thanks  and 
appreciation  to  Professor  Roger  Adams  for  the  sug- 
gestion of  this  problem  and  for  the  interest  shown 
therein. 


TABLE  OF  CONTENTS 


■ 


Page 


I.  INTRODUCTION  1 

II.  HISTORICAL  PART  1 

III.  THEORETICAL  PART  5 

IV.  EXPEREJEI^’TAL  PART  8 

A.  Preparation  of  Catalysts  8 

I.  Colloidal  Platinum  8 

II.  Platinum  Black  9 

a.  Method  of  Feulgen  9 

b.  Sodium  Nitrate  Fusion  9 


B.  Preparation  of  p-Dimethylamino phenol  and  Hydrochloride  10 


C.  Preparation  of  Acetyl-p-dimethylaminophonol  10 

D.  Reduction  Experiments  10 

I.  With  p-Dimethylamino  phenol 10 

a.  Colloidal  Platinum  10 

b.  Platinum  Black  11 


II.  With  p-Dimethylaminophenol  Hydrochloride  11 

a.  Colloidal  Platinum  11 

b.  Platinum  Black  12 


E.  Description  of  Products  12 

I.  Dimethylamino cyclohexane  12 

II.  p-Dimethylaminocyclohexanol  13 


V.  SUIvmRY 14 

VI.  BIBLlOGRilPHY 15 


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The  object  of  this  investigation  was  to  develop  a suitable  method 
for  the  preparation  of  dialkylaminocyclohexanols. 

The  plan  ?;as  to  prepare  these  alcohols  and  then  condense  them  with 
acid  chlorides  to  give  the  esters  of  benzoic  and  p-aniinobenzoic  acids.  These 
aminoalcohols,  being  aliphatic  in  nature,  should  produce  esters  v/hich  possess 
local  anaesthetic  properties,  due  to  the  similarity  in  structure  v;ith  cocaine 
and  novocaine. 


This  report,  hov/ever,  v;ill  deal  only  with  a study  of  the  preparation  ofp- 
dimethylaminocyclohexanol  by  the  catalytic  reduction  of  p-dinethylaminophenol . 
This  aminoalcohol  has  not  been  prepared  before,  so  that  it  is  of  interest  to 
learn  its  physical  constants. 


L.  Brunei  (l)  prepared  o-diethylaminocyclohexanol  by  the  action  of  diethylamine 
on  the  oxide  of  o-cyclohexanediol,  the  reaction  proceeding  as  follow’s: 


It  is  hoped  that  within  the  next  year  the  ortho,  meta  and  para 


dimethylaminocyclohexanols  as  v;ell  as  the  diethyl  derivatives  will  be  prepared. 


II.  HISTORICAL  PART 


To  date,  only  one  dialkylamino cyclohexane 1 has  been  prepared. 


By  similar  reactions  he  also  prepared  o- amino cyclohexanol  and  o-ethylamino- 


cyclohexanol,  using  respectively,  ammonia  and  ethylamine. 


1. 


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-2- 

Osterberg  and  Kendall  (2)  also  prepared  o-diethylaminocyclohexanol. 
They,  however,  dehydrated  cyclohexanol  and  obtained  tetrahydrobenzene.  To 
this  they  added  hypo  chlorous  acid  giving  o-chloro  cyclohexanol,  v/hich  was  then 
condensed  v/ith  diethylamine  to  give  the  desired  compound. 

In  1894  Moyes  and  Ballard  (3)  studied  the  action  of  nitrous  acid 
on  alkylarcines.  From  1.4  diamino cyclohexane  they  obtained  p-amino cyclohexanol. 

Skita  and  Rolfes  (4),  by  means  of  colloidal  platinum,  reduced 
acetanilide,  phenacetin  and  the  acetotoluides  to  the  corresponding  acetylcyclo- 
hexyloniines.  Anisidine  and  phenetidine  in  the  presence  of  hydrochloric  acid 
gave  both  cyclohexylamine  and  dicyclohexylamine,  the  ethereal  group  being 
readily  removed. 

These  authors  also  reduced  the  three  aminophenols  in  the  presence 
of  acetic  and  hydrochloric  acids.  From  the  meta  and  para  compounds  they  ob- 
tained both  the  mono-  and  dicyclohexylamines . With  the  ortho  isomer,  however, 
they  also  obtained  dodekahydrophenoxazine,  which  probably  results  from  the 
condensation  of  tv;o  molecules  of  o-tuninophenol  and  the  subsequent  reduction 


of  the  condensation  product. 

CH.  NH  CHi 

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V V V 

These  investigators  did  not  attempt  to  stop  at  the  aminoalcohol  stage,  but 
continued  the  reduction  until  the  theoretical  amount  of  hydrogen,  necessary 
to  carry  the  reduction  to  the  cyclohexylamine  stage,  had  been  absorbed. 


In  a previous  paper,  Skita  (5)  observed  that  in  reducing  aniline 
by  nesjis  of  colloidal  platinum  in  acetic  acid  solution,  he  could  control  to 
some  extent  the  formation  of  the  mono-  and  dicyclohexylamines,  thru  the  ad- 
dition of  hydrochloric  acid.  The  yield  of  mono cyclohexylamine  is  thereby 


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As  regards  the  hydrogenation  of  phenols  by  means  of  platinum  to 
the  cyclohexaiiol  derivatives,  not  much  work  has  been  done.  Vavon  and  Detrie 
(6)  reduced  phenol  in  glacial  acetic  acid  solution  using  platinum  black  as 
the  catalyst.  They  found  that  the  reduction  proceeded  very  readily.  Hovirever, 
only  a sixty-six  percent  yield  of  cyclohexanol  was  obtained,  the  remainder 
being  further  reduced  to  cyclohexane.  These  investigators  further  observed 
that  the  masking  of  the  phenolic  group,  8,s  for  example,  the  formation  of  ^ 
ether,  exerted  a restraining  influence  upon  the  speed  of  the  reduction.  Ex- 
periments in  this  laboratory  have  shown  that  by  means  of  platinum  black,  pre- 
pared by  the  fusion  of  chlorplatinic  acid  with  sodium  nitrate  (15),  phenol 
could  be  hydrogenated  in  alcoholic  solution  to  give  a theoretical  yield  of 
cyclohexanol,  the  hydrogen  being  absorbed  very  readily. 

Further  literature  on  the  reduction  of  the  benzene  nucleus  is  very 
meager.  In  1^12  V/illstatter  and  Hatt  (7), using  platinum  black,  reduced  ben- 
zene, toluene  and  durol  to  the  hexahydro  derivatives.  They  also  reduced  phenol, 
obtaining  results  which  are  comparable  to  those  of  Vavon  and  Detrie,  mentioned 
above.  With  aniline,  Willstat ter  obtained  a mixture  of  the  mono-  and  dicyclo- 
hexylamines. 

Skita  and  Meyer  (8)  reduced  the  benzene  nucleus  in  benzene,  toluene 
and  benzoic  acid  thru  the  use  of  colloidal  platinum.  In  reducing  aromatic 
aldehydes,  Skita  and  Brunner  (9)  observed  that  the  reduction  did  not  stop  at 
the  alcohol  stage,  but  continued  to  the  saturated  hydrocarbon,  the  benzene 
nucleus  being  reduced  as  v/ell  as  the  alcohol  group.  Thus  cinnamyl  aldehyde 
gives  both  cyclohejcylpropane  and  cyclohexylpropyl  alcohol. 

Willstatter  and  Jaquet  (10)  in  I9I8,  published  a paper  concerning 
the  hydrogenation  of  aromatic  compounds  by  means  of  platinum  containing  oxygen. 


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They  observed  that  in  reducing  phthalic  and  naphthalic  anhydrides  by  the  use 
of  platinum  black,  the  absorption  of  hydrogen  stops  after  only  a short  time. 

The  fact  that  the  reduction  begins  at  all  seems  to  be  due  to  the  presence  of 
oxygen  in  the  fresh  catalyst.  Their  experiments  indicate  that  the  tv;o  cata- 
lysts; namely,  platinum  containing  oxygen  and  the  same  free  from  oxygon,  are 
possessed  of  widely  different  characteristics.  Thus,  by  the  frequent  loading 
of  their  catalyst  Vifith  oxygen,  they  were  able  to  hydrogenate  phthalic  anhydride, 
naphthalic  anhydride  and  phthalimide  v/ith  ease. 

By  completely  exhausting  the  platinum  of  its  oxygen,  v/hich  these 
authors  did  by  shaking  the  catalyst  in  an  atmosphere  of  hydrogen  for  thirty 
hours,  they  were  unable  to  reduce  even  such  easily  reduced  compounds  as  the 
olefines.  Hov/ever,  the  need  of  oxygen  in  reductions  seems  to  be  dependent 
upon  the  ease  of  reduction  of  the  substance  in  question.  Thus,  for  the  reduc- 
tion of  an  olefine,  the  catalyst  need  not  possess  nearly  so  much  oxygen  as 
in  the  reduction  of  a benzene  nucleus,  due  to  the  fact  that  the  latter  is  so 
difficultly  reduced.  With  such  difficultly  reduced  substances,  the  oxygen 
content  of  the  catalyst  is  very  quickly  depleted, 

Y/illstatter  in  a very  recent  paper  (11)  explains  catalytic  reduc- 
tion as  due  to  the  formation  of  a peroxide  with  the  metal  bivalent  and  then  a 
combined  hydride  and  peroxide  with  the  metal  quadrivalent,  thereby  effecting 
the  transfer  of  the  hydrogen.  The  following  equations  show  the  probable  re- 
lations; 


As  the  hydrogen  is  split  off,  some  oxygen  is  also  removed  in  the  form  of  v;ater, 
thus  accounting  for  the  v;ell  knov/n  fact  that  the  catalyst  slov/ly  becomes  in- 


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active.  Shaking  with  air,  however,  will  often  revive  its  activity, 

Skita  (12)  doubts  the  above  mechanism  due  to  the  fact  that  in 
hydrogenating  aromatic  compounds  by  means  of  colloidal  platinum,  oxygen  was 
found  to  be  unnecessary.  This  investigator  shook  colloidal  platinum  in  an 
atmosphere  of  hydrogen  for  thirty  hours,  as  V/illstatter  had  done  v;ith  platinum 
black.  Whereas  Willstatter  found  his  preparation  was  inactive,  Skita  observed 
that  his  v;ould  reduce  phenol  to  cyclohexanol,  Willstatter  also  observed  that 
his  active  catalyst  would  set  iodine  free  from  iodides  due  to  its  oxidative 
properties.  Skita,  thereupon,  added  potassium  iodide  to  a preparation  of  col- 
loidal platinum,  thus  being  assured  of  an  oxygen  free  catalyst.  At  ordinary 
temperatures  this  catalyst  proved  inactive,  but  upon  heating  to  50-60°  C,  the 
reduction  proceeded,  but  only  one-eighth  as  fast  as  normally.  These  facts  led 
Skita  to  believe  the  possibility  of  some  other  mechanism  than  the  one  mentioned 
above.  He  does  not,  however,  claim  to  have  proven  that  the  above  mechanism 
does  not  hold. 

III.  THEORETICAL  PART 

The  only  method  v/hich  seemed  at  all  promising  for  the  preparation 
of  this  series  of  dialky lamino  alcohols,  especially  as  regards  the  preparation 
of  the  meta  and  para  derivatives,  vras  the  catalytic  reduction  of  the  corre- 
sponding dialky laminopheno Is  thru  the  use  of  the  platinum  metals. 

The  only  reported  reduction  of  aminophenols  led  to  the  formation 
of  mono-  and  dicyclohexylamine  and  in  addition,  in  the  case  of  the  ortho  isomer, 
dodekahydrophenoxazine.  It  was  thus  thought  possible  that  the  above  reduction 
might  be  stopped  at  the  alcohol  stage  after  the  theoretical  absorption  of 
hydrogen.  Furthermore,  since  Skita  observed  that  the  addition  of  a small 
amount  of  hydrochloric  acid  hindered  the  splitting  off  of  the  amino  residue, 


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-6- 

and  since  the  addition  of  the  acid  would  raake  the  base  v;ater  soluble,  it  seemed 

advisable  to  v/ork  with  the  hydrochloride  of  the  free  base. 

However,  before  the  reduction  of  the  hydrochloride  was  attempted, 

it  seemed  worth  while  to  attempt  the  reduction  of  the  free  base.  Thus,  it  v/as 
attempted  to  reduce  p-dimethylaminophenol,  both  in  aqueous  suspension  and  in 
alcoholic  solution.  In  the  former  case  both  colloidal  platinum  and  platinum 
black  were  tried  and  in  the  latter  case,  platinum  black  alone  was  tried.  In 
no  instance,  however,  was  the  reduction  successful. 

As  regards  the  reduction  of  the  hydrochloride,  it  v/as  found  that 
the  addition  of  the  theoretical  amount  of  hydrochloric  acid  to  the  free  base 
was  not  effective,  either  with  colloidal  platinum,  prepared  by  the  method  of 
Skita  and  Meyer  (I3)  or  v/ith  the  black,  prepared  by  the  method  of  Feulgen  (14) 
or  by  sodium  nitrate  fusion  (15) • 

If,  however,  the  free  hydrochloride  was  first  isolated  by  the  pre- 
cipitation of  the  base  from  dry  ether  by  meajis  of  dry  hydrochloric  acid  gas, 
the  reduction  did  proceed,  but  only  very  slov/ly.  With  colloidal  platinum  the 
main  product  is  dimethylamino cyclohexane,  only  a trace  of  p-dimethylaminocyclo- 
hexanol  being  obtained. 

The  next  attempt  was  with  platinum  black  prepared  according  to  the 
method  of  Feulgen  and  it,  too,  proved  a failure.  In  this  case  the  reduction 
did  not  proceed  at  all.  V/hen  platinum  black,  prepared  by  the  sodium  nitrate 
fusion  method  was  used,  the  reduction  was  effected,  but  only  very  slowly.  The 
platinum  black  at  first  seemed  to  form  a colloidal  suspension  which  was  de- 
stroyed after  the  entrance  of  approximately  one-half  the  theoretical  amount  of 
hydrogen.  From  this  point  on,  no  hydrogen  was  absorbed.  The  coagulation 
without  doubt  results  from  the  cyclohexanol  formed  in  the  reduction.  It  was 
attempted  to  overcome  this  difficulty  by  using  both  95  percent  alcohol  and 
50  percent  alcohol  instead  of  water  as  the  solvent.  However,  the  attempts  with 


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-7- 


these  two  modifications  proved  no  better  than  that  in  which  v;ater  alone  v;as 
used.  The  yield  in  all  three  cases  was  practically  the  same,  consisting  of 
approximately  20  percent  p-dicethylaminocyclohexanol,  25  percent  dimethylamino- 
cyclohexane,  and  approximately  2 percent  of  cyclohexanol. 

As  stated  above,  the  reduction  proceeds  very  slowly.  The  probable 
cause  for  this  is  that  p-dimethylaminophenol  is  very  easily  oxidized,  its  sol- 
ution turning  black  even  on  standing  in  the  air.  The  same  applies  to  the 
hydrochloride.  Since  the  aninophenol  is  so  easily  oxidized,  the  oxygen  content 
of  the  platinum  is  very  quickly  depleted,  thus  causing  the  catalyst  to  lose 
its  activity.  This  is  substantiated  to  some  extent  by  the  fact  that  if  fresh 
platinum  black  is  added  to  a colorless  solution  of  the  hydrochloride  in  water, 
the  latter  being  kept  in  an  atmosphere  of  hydrogen,  the  solution  will  turn 
brown  in  the  immediate  vicinity  of  the  catalyst.  This  indicates  that  an  oxi- 
dation is  taking  place  and  seems  to  corroborate  V/illstatter ' s conclusions 
regarding  the  necessity  of  oxygen  in  active  platinum.  The  platinum  black  in 
this  case  cannot  be  revivified  by  shaking  vdth  air  as  in  the  case  of  the  reduc- 
tion of  many  other  organic  compounds.  The  same  explanation  applies  here; 
namely,  the  oxygen  is  taken  from  the  platinum  as  fast  as  the  latter  absorbs  it 
from  the  air.  This  seems  to  be  substantiated  by  the  fact  that  v;hen  the  color- 
less solution  emd  inactive  catalyst  are  shaken  v.dth  air  the  former  quickly  turns 
black. 

That  the  amino  group  might  exert  a poisoning  effect  on  the  cata- 
lyst is  very  improbable,  especially  since  in  the  above  case  it  has  been  covered 
in  the  form  of  a hydrochloride.  Certainly  the  phenolic  group  does  not  exert 
an  undesirable  effect,  since  phenol  reduces  v/ith  great  ease. 

The  probable  reason  why  the  platinum  black,  prepared  by  sodium 
nitrate  fusion,  will  effect  the  reduction,  whereas  that  prepared  by  the  method 

J 


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-8- 


of  r’eulgen  will  not,  is  because  the  former  undoubtedly  possesses  much  more 
oxygen.  This  explanation  is  supported  by  the  fact  that  the  former  will  reduce 
salicylaldehyde  about  twenty  times  as  fast  as  the  latter  and  will  retain  its 
activity  much  longer. 

Since  the  alcohol  group  is  reduced  off  to  an  extent  of  50  percent, 
it  seemed  advisable  to  cover  this  group  by  some  means,  such  that  the  free 
hydroxyl  group  could  be  easily  regenerated.  For  this  purpose  the  acetyl  de- 
rivative of  p-dimethylciminophenol  was  prepared.  An  attempt  to  reduce  this 
substance  in  alcoholic  solution,  using  the  more  active  platinum  black,  pre- 
pared by  sodium  nitrate  fusion,  proved  unsuccessful. 

Thus,  the  only  satisfa.ctory  method  for  reducing  p-dimethylamino- 
phenol  seems  to  be  the  hydrogenation  of  the  isolated  hydrochloride  in  aqueous 
solution  by  means  of  platinum  black  prepared  by  the  sodium  nitrate  fusion 
method.  This  study  will  be  continued  thru  the  coming  year,  and  it  is  hoped 
that  the  method  v/ill  be  improved.  This  will  probably  be  accomplished  by  the 
choice  of  a better  solvent,  since  the  latter  seems  to  exert  a strong  influence 
upon  the  reduction. 

IV.  EXPERUmiTKL  PA.RT 
A.  Preparation  of  Catalysts 
I.  Colloidal  Platinum 

The  colloidal  platinum  was  prepared  according  to  Skita  and  Meyer 
(13).  One-half  gram  of  gum  arabic  v/as  dissolved  in  water  by  grinding  in  a 
mortar  and  adding  from  time  to  time  a small  amount  of  water.  Then  the  desired 
amount  of  10  percent  chlorplatinic  acid  solution  v/as  added  and  the  solution 
diluted  to  the  desired  volume.  The  resulting  solution  was  inoculated  by  add- 
ing a small  amount  of  colloidal  platinum,  prepared  by  reducing  0.5  to  1 cc. 


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n. 

Ir 


-9- 

of  chlorplatinic  acid  in  an  alkaline  solution  v/ith  hydrazine  hydrochloride  or 
sulfate.  This  solution  \ms  shaken  with  hydrogen,  v/hereupon  the  platinum  v/as 
reduced,  giving  a colloidal  solution.  The  substance  to  be  reduced  v/as  then 
added. 

II.  Preparation  of  Platinum  Black. 

(a)  Method  of  Feulgen  (14) 

Five  grams  of  chlorplatinic  acid  v/as  dissolved  in  5 cc.  of  v/ater, 
and  to  this  v/as  added  7 cc.  of  40  percent  formaldehyde  solution.  The  latter 
v/as  then  cooled  in  an  ice  bath  and  a solution  of  5 gr.  of  sodium  hydroxide 
in  10  cc.  of  v/ater  v;as  added  drop  by  drop  v/ith  vigorous  stirring.  Care  should 
be  exercised  here  as  the  reaction  becomes  vigorous  find  foams  excessively  upon 
too  rapid  an  addition.  The  reaction  mixture  v/as  allov/ed  to  stand  for  one-half 
hour  at  room  temperature.  The  temperature  was  then  raised  to  55°  C.  and  kept 
there  for  one-quarter  hour,  whereupon  it  was  diluted  v/ith  250  cc.  water.  The 
Bother  liquor  was  decanted  and  more  water  added,  the  latter  being  acidified 
with  acetic  acid  to  prevent  the  formation  of  a colloidal  suspension.  The  plat- 
inum black  was  finally  filtered  off  and  dried  in  vacuo  over  sulfuric  acid. 

(b)  Sodium  Ilitrate  Fusion  Method  (15) 

Five  grams  of  chlorplatinic  acid  was  dissolved  in  IOO-I5O  cc.  of 
v/ater  and  to  this  v/as  added  approximately  50  gr.  of  sodium  nitrate.  The  solu- 
tion was  evapora.ted  to  dryness  and  then  fused.  It  v/as  kept  at  this  tempera- 
ture until  the  vigorous  evolution  of  gas  ceased.  The  melt  was  cooled  and  ex- 
tracted Y/ith  hot  water.  The  platinum  black  v/as  then  filtered  off,  thoroughly 
v/ashed  and  finally  dried  in  vacuo  over  sulfuric  acid.  The  final  product  is 
of  a brown  color  and  when  shaken  v/ith  hydrogen  in  an  aqueous  or  alcoholic 
solution  produces  a colloidal  suspension  which  v/ill  again  coagulate  upon  shak- 
ing v/ith  air. 


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-10- 

B.  Preparation  of  p-Diinethylaminophenol  £ind  its  Hydrochloride 

To  prepare  the  above  the  free  base  \ms  first  isolated  from  the 
oxalate  salt  which  is  obtained  as  a by-product  in  the  manufacture  of  p-methyl- 
aminophenol,  which  is  used  as  a developer. 

To  182  gr.  (0.5  ^nol.)  of  p-dlmethylaminophenol  oxalate  was  added 
enough  water  to  make  stirring  easy.  Forty  gr.  (1  mol.)  of  sodiin  hydroxide, 
dissolved  in  approximately  100  cc.  of  water,  v/as  added  T/ith  vigorous  stirring 
to  prevent  clumping.  This  mixture  was  extracted  with  benzene  and  then  filtered. 
The  benzene  layer  \?as  separated  and  distilled  in  vacuo,  the  i^ree  base  distill- 
ing over  at  125°  C.  at  about  7*8  imn.  pressure.  The  distillate  should  be 
rapidly  cooled  as  it  oxidizes  very  readily  upon  exposure  to  air. 

To  prepare  the  hydrochloride  the  free  base  was  dissolved  in  dry 
ether  cooled  in  ice  and  diT’  hydrochloric  acid  gas  passed  in. At  first  the  hydro- 
chloride came  down  as  a sticky  mass  which  became  crystalline  as  an  excess  of 
acid  was  passed  in.  The  product  was  then  filtered,  washed  vath  dry  ether  and 
finally  dried  in  the  air, 

C.  Preparation  of  Acetyl-p-dimothylsmiinophenol 

The  acetyl  derivative  of  p-dimethylaminophenol  v/as  prepared  by 
mixing  together  30  gr.  of  the  free  base  with  35  gr.  of  acetic  anliydride  and 
heating  on  the  steam  bath  for  one  hour.  The  reaction  mixture  was  then  cooled 
and  poured  into  a small  amount  of  ice  water.  The  product  was  filtered  off, 
thoroughly  washed  \d.th  water  and  finally  recrystallized  from  butyl  alcohol, 
giving  pretty  pink  crystals  melting  at  78°  C. 

D.  Reduction  Experiments 

I.  With  p-Dimethylaminophenol 
(a)  Colloidal  Platinum 

To  a preparation  of  colloidal  platinum  as  described  above  and  con- 


U •Xf 


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1 


-11- 

taining  0.5  gr.  platinvm,  5 gi*-  of  p-dlmethylaminophenol  Viras  added  and  the 
voliune  of  liquid  increased  to  approximately  50  cc.  Hydrogen  was  then  passed  in 
under  a pressure  of  30-35  Ihs.,  but  none  was  absorbed. 

(b)  Platinum  black 

To  a suspension  of  5 gr.  of  the  free  base  in  50  cc.  water  was  added  0.5 
gr.  platinum  black,  prepared  by  the  sodium  nitrate  fusion  method.  The  reaction 
mixture  v;as  then  shaken  for  one  hour  v;ith  hydrogen  under  a pressure  of  30-35 
lbs.  as  above  but  no  absorption  took  place.  The  same  was  repeated  using  50  cc. 
of  alcohol  in  place  of  the  water,  but  with  no  better  results. 

Another  series  of  experiments  on  the  free  base  was  tried.  Here  the 
theoretical  amount  of  hydrochloric  acid  was  added  to  take  the  base  into  solu- 
tion, These  attempts  proved  unsuccessful  v/ith  colloidal  platinum  and  the  two 
platinum  blacks. 

The  reduction  of  the  acetyl  derivative  of  p-dimeth3'-lamino phenol  was  at- 
tempted, using  platinum  black,  prepared  by  the  sodium  nitrate  fusion  method 
and  alcohol  as  the  solvent.  It  likewise  proved  unsuccessful. 

II.  With  p-Dimethylaminophenol  Hydrochloride 
(a)  Colloidal  Platinum 

To  a preparation  of  colloidal  platinum,  containing  0.5  gr.  plati- 
num, 12  gr.  of  free  hydrochloride  was  added  and  the  solution  diluted  to  about 
60  cc.  This  was  then  shaken  with  hydrogen  under  a pressure  of  30-35  lbs.  When 
approximately  one-half  the  theoretical  amount  of  hydrogen  had  been  absorbed, 
the  reaction  stopped.  The  colloidal  platinum  vra.s  precipitated  by  acidifying 
strongly  with  hydrochloric  acid  and  heating  to  boiling.  The  platinum  was  fil- 
tered off  and  the  filtrate  evaporated  to  25-30  cc.  in  vacuo.  Solid  sodium 
hydroxide  was  then  added  to  saturation  and  the  basic  layer  extracted  with  ether 
or  benzene.  The  extract  was  then  distilled  in  vacuo,  5 gr.  of  dimethylamino- 


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cyclohexane,  7;ith  a small  amount  of  the  desired  alcohol,  being  obtained.  The 
former  distilled  over  at  52-54-°  C.  at  17  mm.  and  the  latter  at  125°  C. 

(b)  Platinum  Black 

To  a solution  of  12  gr.  of  the  hydrochloride  in  60  cc.  of  water 
was  added  0.5  gr.  of  platinum  black,  prepared  according  to  Feulgen.  Hydrogen 
was  then  passed  in  under  a pressure  of  30“35  lbs.,  but  no  absorption  took 
place. 

The  same  was  repeated,  using  42  gr.  of  the  hydrochloride  in  120  cc. 
of  water  and  2 gr.  of  platinum  black,  prepared  by  the  sodium  nitrate  fusion 
method.  The  reduction  proceeded,  but  only  very  slowly.  As  v/ith  colloidal 
platinum,  the  absorption  stopped  in  midreaction.  To  attain  this  stage  re- 
quired from  10  - 14  hrs.  At  this  point  the  platinum  black,  which  at  first 
assumed  a colloidal  state,  flocked  out.  Upon  working  up  the  reaction  mixture 
as  before  11  gr.  of  dimethylamino cyclohexane,  3 gr.  of  cyclohexanol  and  8 gr. 
of  p-dimethylamino cyclohexanol  were  obtained.  The  cyclohexanol  steam  distilled 
over  upon  evaporating  the  solution  in  vacuo.  The  p-diraethylaminocyclohexanol 
distilled  over  at  99.5  " 100°  a-'t  7 pressure. 

Similar  runs  virere  made  using  95  percent  and  50  percent  alcohol  as 
the  solvents.  The  results  were  practically  the  same  as  those  obtained  above. 

E.  Description  of  Products 

I.  Dimethylamino cyclohexane 

This  compound  has  already  been  prepared  but  its  physical  constants 
do  not  agree  closely  with  those  reported  in  the  literature.  Therefore,  it 
seemed  of  value  to  determine  the  following  constants: 

(1)  Boiling  Point  l60®  C. 

(2)  Specific  Gravity  0.84? 

(3)  Index  of  Refraction  1.4528 


250 


I 


“13- 

The  hydrochloride  upon  recrystallization  fron  butyl  alcohol  melted  at  238°  C. 
Analysis;  ,Subs.  O.3O93  gr.,  17.00  cc.  O.IO96K  AgllO^ 

Calc,  .for  CqH^^N.HCI:  01,21.69^;,  Found:  21.36;'i 

Subs.  0.4793  gr.,  43.71  cc.  O.O843N  acid, 

Calc,  for  CgH^^N;  N,  11.02^,  Found;  10.76/% 

II.  p-Dimethylaminocyclohexanol 

As  stated  above,  this  substance  has  never  been  prepared  before.  It 
is  a colorless  and  very  viscous  liquid  possessing  the  following  physical  con- 


stants: 

(1)  Boiling  Point  228°  C. 

(2)  Specific  Gravity  O.983 


(3)  Index  of  Refraction  ) 1.4859 

The  hydrochloride  is  very  hygroscopic.  Indeed,  it  absorbs  moisture 
from  the  atmosphere  so  fast  that  it  is  impossible  to  get  the  substance  into 
a melting  point  tube.  After  careful  drying  in  a vacuum  oven  at  100°  C.  it  was 
analy  zed,  Analy  sis: 

Subs.  0,2844  gr.,  14.53  cc,  0,1096  N AgNO^ 

0.4702  gr.,  34.3  cc.  N2  (32°  C.,  739.4  mm.) 

Calc,  for  C3H1.7ON.HCl:  Cl,  19.85^;  N,  7.80^, 

Found:  Cl,  I9.76/0;  N,  7.?2f» 


ry.sm 


-14- 


V.  smaiARY 


The  reduction  of  the  hydrochloride  of  p-dinethylarninophenol  was 
effected  catalytically  by  means  of  platinum  black,  prepared  by  the  fusion  of 
chlorplatinic  acid  with  sodixam  nitrate. 

The  products  of  the  above  reduction  in  aqueous  solution,  consisted 
of  approximately  equal  ar*iounts  of  p-dimethylaminocyclohexanol  and  dimethyl- 
amino  cyclohexane. 

The  observations  led  to  the  conclusion  that  the  slowness  with 
v/hich  the  reduction  proceeds  was  due  to  the  fact  that  the  oxygen  content  of 
the  platinum  was  very  quickly  and  seriously  depleted  by  the  easily  oxidizable 
p-dimethylaminophenol  hydrochloride. 

p-Dinethylaminocyclohexanol,  which  has  not  been  previously  de- 
scribed, was  obtained  as  a colorless,  viscous  liquid  and  its  physical  constants 


were  determined 


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-15- 


VI.  BIBLlOGPulPHY 

1.  Brunei  - Ann.  Chim.  (8)  6,252  (1905) 

2.  Osterberg  and  Kendall  - J.  An.  Chem.  Soc,  43,  1370  (1921) 

3.  Noyes  and  Ballard  - Ber.  27,  1450  (1894) 

4.  Skita  and  Rolfes  - Ber,  53»  1242  (1920) 

5.  Skita  and  Berendt  - Ber.  52,  15^9  (^919) 

6.  Vavon  and  Detrie  - Compt,  rend.  172,  1231  (1921) 

7.  Y/illstatter  and  Hatt  - Ber.  45,  1471  (1912) 

8.  Skita  and  Meyer  - Ber.  45,  3589  (1912) 

9.  Skita  and  Brunner  - Ber,  48,  1685  (1915) 

10.  Willstatter  and  Jaquet  - Ber.  51,  76?  (1918) 

11.  Willstatter  and  ?/aldschmidt-Leitz  - Ber.  54-,  113  (1921) 

12.  Skita  - Ber.  55,  139  (1922) 

13.  Skita  and  Meyer  - Ber.  45,  3579  (1912) 

14.  Feulgen  - Ber.  54,  36O  (I92I) 

15.  Adams  and  Voorhees  - Thesis,  University  of  Illinois  (1922) 


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